1. Field of the Invention
This invention relates to a method and apparatus for reducing emissions in combustion products resulting from a two-stage continuous combustion process.
2. Description of Prior Art
Many conventional combustion processes use staged combustion wherein fuel and primary air are introduced into a primary combustion chamber to form a fuel-rich mixture and secondary air is introduced in a secondary combustion zone. For example, U.S. Pat. No. 5,472,339 discloses a baffle member which divides a combustion chamber into first and second regions. A fuel-rich mixture of gas and primary air is injected through an inshot burner and a combustion flame is drawn into the combustion chamber by an induced draft blower which also introduces secondary combustion air. The baffle member channels the flame and secondary combustion air into a convergent flow path and over the baffle member to create turbulence, which enhances mixing between the fuel-rich flame and secondary combustion air within the second region of the combustion chamber, which is downstream with respect to the baffle member.
U.S. Pat. No. 5,244,381 discloses an inshot burner mounted within a central opening that allows secondary air to pass into the combustion chamber. The secondary air is directed by a frustro-conical member into the combustion zone for enhancing the combustion process. The frustro-conical member spans from an upstream side of an exit plane of the inshot burner to a downstream side of the exit plane. A target plate is positioned near the discharge end of the inshot burner. The target plate transfers heat from the flame to rods affixed to a face of the target plate.
U.S. Pat. No. 5,597,301 discloses a burner emission device that includes a stack of perforate metal sheets positioned in a flow path of a flame, which enhances turbulence.
It is apparent from the known conventional technology that there is a need for a two-stage burner apparatus and method which reduces nitrogen oxides and which can be retrofitted into many existing burner devices.